Cylindrical containers intended for retaining chemicals, industrial materials, and the like are structured in generally common fashion by fabricators. Their size and the materials from which they are formed vary substantially. However, those formed of plastic, cellulosic or fibrous materials vary in capacity from 3 gallon plastic pails to 55 gallon fiber, plastic or metal drums. Generally, to enhance container strength, as well as to facilitate the attachment of a lid, the rims of the pails or drums are reinforced with annular metal chimes formed having a rim bead and an inwardly-extending region or groove just below the bead. For most designs, the formation of the groove effects a deforming securement of the rim to the drum wall. Lids typically enclosing the drums are formed as stamped metal or plastic components which are secured over the rim-chime assemblies with metal split ring clamps having a channel or U-shaped cross-section, the lower inwardly turned side or edge of which engages the rim groove and the upper side of which abuts over the lid top. An overcenter lever generally is used to draw the ends of the split ring structure together. For many packaging, transportation, and incineration container applications, industrial users of such structures have sought to avoid metal components such as lids and lid retainers, for example split ring clamp devices. These metal devices do not burn, are prone to corrode or, importantly, to insert minute metallic contaminants with material packaged within the containers. While plastic lids have been developed, for example as described in U.S. Pat. No. 4,718,571, the development of a plastic clamping ring which remains competitive in terms of both cost and securement performance has been elusive to investigators.
Fiber based drums as well as plastic containers, when filled, will be warehoused and transported by personnel employing hand carts, forklifts and like devices. Thus, from time to time, the filled containers may accidentally be dropped varying distances upon hard surfaces. Upon the occurrence of such dropping accidents, the containers, typically weighing in the range of 50 to 500 pounds, will be highly strained and somewhat deformed during impact. To assure a secured retention of the lid retained drum contents, designs for the lid securing structures are tested. For example, specifications have been promulgated by a variety of commercial, international and government entities and the United States Department of Transportation (DOT), Research and Special Programs Administration. See generally 49 CFR CH. (Oct. 1, 1988 Edition), Section 178.244-2. Typically, drop tests are called for by the test procedures wherein samples taken at random are filled with dry finely powdered material to authorized net weight and closed as for use. The containers, inter alia, must withstand a drop tests of varying heights upon specified parts without leakage or serious rupture. In one such drop, the top chime is directed diagonally onto solid concrete. In another test, the bottom of the container is dropped diagonally such that the bottom chime contacts solid concrete.
While drum-lid assemblies along with split clamping rings have met the specifications as above, heretofore, such specifications have been met with metal split clamp rings. These metal rings generally are formed of multiple parts, with the clamping components being riveted to the metal channel shaped ring portions. This multitude of parts may vary in number, for example, from about 7 to 13. Implementation of the devices with all-plastic material requires the elimination of parts to achieve a cost competitiveness. Additionally, the plastic devices should be capable of meeting securement specifications, such as those discussed above. However, it has been the experience of investigators that plastic split ring clamping assemblies are prone to fail the drop-based securement or drop tests.